package com.tmsps.ne4spring.utils;

/**
 * 生成工具
 * 
 * @author zhangwei 396033084@qq.com
 *
 */
public class GenerateLongUtil {

	private long workerId;
	private long datacenterId;
	private long sequence;

	private static GenerateLongUtil instance = new GenerateLongUtil(1, 1, 1);

	public static GenerateLongUtil getInstance() {
		return instance;
	}

	private GenerateLongUtil(long workerId, long datacenterId, long sequence) {
		// sanity check for workerId
		if (workerId > maxWorkerId || workerId < 0) {
			throw new IllegalArgumentException(
					String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
		}
		if (datacenterId > maxDatacenterId || datacenterId < 0) {
			throw new IllegalArgumentException(
					String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
		}
		// System.out.printf(
		// "worker starting. timestamp left shift %d, datacenter id bits %d,
		// worker id bits %d, sequence bits %d, workerid %d",
		// timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits,
		// workerId);

		this.workerId = workerId;
		this.datacenterId = datacenterId;
		this.sequence = sequence;
	}

	private long twepoch = 1288834974657L;

	private long workerIdBits = 5L;
	private long datacenterIdBits = 5L;
	private long maxWorkerId = -1L ^ (-1L << workerIdBits);
	private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
	private long sequenceBits = 12L;

	private long workerIdShift = sequenceBits;
	private long datacenterIdShift = sequenceBits + workerIdBits;
	private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
	private long sequenceMask = -1L ^ (-1L << sequenceBits);

	private long lastTimestamp = -1L;

	public long getWorkerId() {
		return workerId;
	}

	public long getDatacenterId() {
		return datacenterId;
	}

	public long getTimestamp() {
		return System.currentTimeMillis();
	}

	public synchronized long nextId() {
		long timestamp = timeGen();

		if (timestamp < lastTimestamp) {
			System.err.printf("clock is moving backwards.  Rejecting requests until %d.", lastTimestamp);
			throw new RuntimeException(String.format(
					"Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
		}

		if (lastTimestamp == timestamp) {
			sequence = (sequence + 1) & sequenceMask;
			if (sequence == 0) {
				timestamp = tilNextMillis(lastTimestamp);
			}
		} else {
			sequence = 0;
		}

		lastTimestamp = timestamp;
		return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift)
				| (workerId << workerIdShift) | sequence;
	}

	private long tilNextMillis(long lastTimestamp) {
		long timestamp = timeGen();
		while (timestamp <= lastTimestamp) {
			timestamp = timeGen();
		}
		return timestamp;
	}

	private long timeGen() {
		return System.currentTimeMillis();
	}

	// ---------------测试---------------
	public static void main(String[] args) {
		GenerateLongUtil worker = GenerateLongUtil.getInstance();
		for (int i = 0; i < 30; i++) {
			System.out.println(worker.nextId());
		}
	}
	
}
